FA-81052 / Music interval and transposition theory / Member archive

Pitch-class set prime form (right-packed): normal form not transposed to zero · case 02

A major triad on D returns [2,6,9]-shaped values rather than [0,3,7].

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Input a list of integers. Compute the right-packed normal form of the set and of its inversion (p -> -p mod 12), transpose each to start on 0, and return whichever is more packed: compare the last value, then the penultimate, and so on toward the second (the original wins ties). Empty input returns []; non-integers return None.

Why this case matters

Set-class labelling depends on prime forms being computed identically for every member of a class.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
oracle 0	`[5, 8, 0]`	`[0, 3, 7]`	Failed

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